The present invention relates to an image pickup assembly and more particularly to a means for mounting a television camera tube in the center of a television camera yoke.
It is known that the geometrical distortion of an image on the image pickup tube is proportional in an amount to the square and the cube of its distance from the central axis of the deflection coil. The axis of the coil must be aligned with the axis of the image pickup tube and the optical axis within close tolerances. The optical axis of the camera and the axis of the coil are aligned with great precision but with the image pickup tube there is difficulty in aligning the picture pickup tube with the coil assembly due to the image pickup tube being manufactured with varying thicknesses and outer diameters. There is also the possibility of damage because the tube is made of glass. Further, if the cameras are slightly shocked in handling or new tubes installed it will cause misregistration and the camera must be recalibrated. Referring to U.S. Pat. No. 4,039,986 of Nakazawa et al, there have been a variety of approaches for mounting the tube in the coils. In FIG. 1 of the referenced patent of Nakazawa et al, elastic material such as gum rubber is used at two points along the tube (not at the remote ends) for mounting the tube. As illustrated in FIG. 2, of the above referenced patent, the elastic material may be embedded in a holder. The elastic material in the prior art has a minimum inner diameter that is smaller than the outer diameter of the pickup tube and depends upon the elasticity to absorb the irregularity of the outer diameter of the pickup tube. These elastic material pieces require a special shape and they are not only expensive to manufacture but are difficult to manufacture with high dimensional precision. This results in difficulty of alignment of the central axis of the coil assembly with that of the image pickup tube. Further, these elastic members are known to wear and the restoring forces may not completely return, making alignment difficult when replacing a new tube or when the camera is shocked in handling. Further as discussed in the referenced U.S. Pat. No. 4,039,986, the image pickup device is mounted using O-rings made of elastic material along the length of the tube. These O-rings have essentially the same problems as the other elastic materials. They are difficult to manufacture with high dimensional precision, are known to wear and the restoring forces may not completely return the tube when shocked in handling or when replacing a tube. An added disadvantage of prior art solutions is that the tubes are not securely held to prevent axial motion with respect to the yoke. This axial motion will cause focus and alignment problems.